Tuesday, July 26, 2011

While many leafhoppers are rather drab in appearance, there are some that aim to dazzle. One of the most colouful found in Ireland is Cicidella viridis. Its yellow head and yellow and green protonum give way to strking wings, a wonderful turquoise in females, but a lot darker (often a blue-purple) in males. They feed on a variety of grasses, sedges and rushes by by inserting two pairs of feeding stylets (modified mandibles and maxillae) into the host plant tissue, injecting saliva, and ingesting fluid (1). This feeding method, common to all Auchenorrhyncha (Cicadas, Spittlebugs, Leafhoppers, Treehoppers, and Planthoppers) presents a particular problem. When sap is ingested, a large volume of excess water is also taken in, which presents a raft of osmotic issues. C. viridis posses an organ called a filter chamber to combat this problem. This rapidly transfers excess water from the initial midgut to the terminal midgut down a transepithelial osmotic gradient (2). The membrane of the filter chamber is composed of a protein known as P25, a member of a family of protieins (MIP) that are permeated by water but not any associated solutes.

One of the most attractive moths to be seen in Ireland, the Six Spotted Burnet (Zygaena filipendulae) is currently on the wing. Flying during the day, this moth has a lazy, almost awkward pattern of flying. The adult wings are a dark, metallic green and spotted with the most delightful deep-red spots, six on each forewing. These six spots distinguish it from its close relative the Narrow Bordered Five Spotted Burnet (Z. lonicerae). The adults feed on flowers of knapweed and scabious plants, with the larvae feeding on birdsfoot trefoil (Lotus corniculatus). The larvae derive a level of protection from their host plant, sequestering the cyanogenic glucosides linamarin and lotaustralin (1). These act as defence compounds against preadtors. These cyanogenic glucosides are integral to Z. filipendulae's life cycle and larvae fed wildtype L. corniculatus showed faster development times than those fed transgenic, acyanogenic plants. Larvae are also capable of de novo synthesis of the cyanogenic glucosides and adult male Z. filipendulae transfer a nuptial gift of the compunds to females during mating, with females showing a preference for males with higher cyanogenic glucosides levels (2).

Friday, July 22, 2011

Plant species that are considered scarce are generally found in places with little disturbance and, by association, little human interference. This is not always the case though. Take for example Greater Quaking-grass (Briza maxima). This attractive plant, with its large, pendulous spikelets, is present in few Irish sites (1). Yet one of these is smack bang in the centre of a major Irish city. As the river Lee makes its way through the city of Cork, some of its quaysides are lined with old wharf timers, used in former times for unloading produce from merchant ships. Surprisingly, on some of these timbers at Union Quay and Morrison Quay, B. maxima proliferates from April to May. The specimen pictured was just observed in all its quaking glory just steps from Trinity foot bridge.

While many sawflies display bold, showy colours on their abdomens, there are also quite a few that are more demure. Take Arge gracilicornis, a rose sawfly. In colour and appearance it resembles a fly, with its dark body and dusky wings. In common with other Arge spp. it also has quite reduced antennae which add to its fly like appearance. In its larval form, however, it is a different story. It has a translucent green body, dotted with vibrant yellow and black spots. A. gracilicornis larvae feed on the edges of rose and related plant leaves, leaving them quite exposed to predation by birds and a range of invertebrates. The spots along the body may act as a warning to predators: it has been shown that starlings (Sturnus vulgaris) avoid feeding on the larvae (1). The body of the larvae are also lined with bristles making them unpalatable. More impressively though, A. gracilicornis larvae, along with other Arge spp. larvae, produce antifeedent chemicals. Ants that bit Arge spp. larvae showed a pronounced lack of co-ordination (2). Extracts from the gut of larvae also exhibited a paralysing effect.

Thursday, July 21, 2011

The Scarlet Pimpernel (Anagallis arvensis) is a common annual of roadsides, cultivated land and dunes, and is most famous for its delicate scarlet flowers (1). These are at the end of straggling stems that are often up to 25 cm in length. The flowers open in the morning and close at mid afternoon, lending it the alternate common name of “Shepherd's Weatherglass”. The plant is a source of a diverse number of natural compounds, with 14 flavanoids, 3 anthocyanins (2), oleanane triterpenes, saponins, flavones and cucurbitacins (3) to name but a few, isolated to date. One of the triterpene saponins isolated from A. arvensis has even been shown to have antiviral activity against the herpes simplex virus and poliovirus (4), proving it to be a useful plant indeed.

Wednesday, July 20, 2011

There's no two ways about it, stinging nettles (Urtica dioica) hurt. Their leaves and stems (which is pretty mush all of them) are lined with time hairs that act as hypodermic needles, injecting a cocktail of chemicals into whatever brushes off them. This induces the stinging sensation associated with them. This would seem to make them unsocial organisms in our eyes, repelling all comers. Yet this is not the case, with many animals readily living with, and even on, U. doica. Take the mirid bug pictured, Grypocoris stysi.

Grypocoris stysi

It can regularly be observed amking its way through the leaves of nettle plants feeding on aphids and the flower heads, impervious to the hairs which, due to the bug's size (c. 6 mm), are easily avoided.

A conspicuous little beetle, with an abdomen that looks all the world like a miniature kiwi fruit, Lagria hirta is most commonly found in sandy places in Ireland, but can be found throughout the country. While the larvae eat detritus, the adults can be found feeding on a variety of flowers such as umbellifers and Compositae (1). L. hirta has a univoltine life cycle, that is it produces just one brood per year. Adults are present for only a short time in summer, whereas the larval stage extends from autumn to spring (2). This adherence to univoltism has been shown to be due in part to larval diapause (or dormancy) (3). It was shown under laboratory conditions that larvae did not pupate if kept at constant temperature. Pupation was only achieved if larvae were reared at 15-20°C, followed by a three moth chilling period of 5°C.

Thursday, July 14, 2011

Wild Thyme (Thymus polystrichus, also Thymus praecox) is an attractive and aromatic, mat forming, perrenial of dry grasslands and heaths (1). Its dense heads of pink-purple flowers are visible now, having appeared in June and persisting until September. It is indigenous to the North Atlantic region of Europe, being found from Iceland, the Faroe Islands, Ireland and Britain to Norway and Greenland (2). A study of the essential oil components of plants from throughout this range revealed 17 chemotypes of T. polystrichus exist, with most diversity of types being found in the plants southern range (Scotland, Ireland and England) (3).

A subject of a previous post, Sciara hemerobioides, was recently observed swarming around False Oat Grass (Arrhenatherum elatius), seemingly feeding on the seeds of the grass, in a coastal area. I find this quite odd, as any references I have found to adult S. hemerobioides feeding have put then feeding on the nectar of umbelliferous plants (1) and adults can only ingest liquids. No mating, or interest in mating, was observed in any of the flies. The all seemed to be actively feeding at the grass seed head.

An impressively sized beetle, the Rose Chafer (Cetonia aurata) certainly doesn't shy away from being noticed. One of the 35 species of scarab beetles present in Ireland (1), its green-bronze thorax and elytra (which also bear white flecks) (2) glints attractively in the sunlight as it buzzes noisily around searching for food. When it does find food it rather clumsily waddles about to get the best point at which to eat it, often knocking itself to the ground with its efforts.

Rose Chafer, Cetonia aurata, feeding on grass seed

They feed upon flowers, nectar, pollen and, in the case of the individual picture, seeds, meaning they pose a threat to agricultural produce (3). Ingeniously, control of C. aurata is achieved by attraction using synthetic floral scents and colours and subsequent trapping (4). C. aurata has shown a particular preference for the colour blue and a scent composed of (E)-Anethol, 3-Methyl eugenol, 1-Phenylethanol and (±)-Lavandulol. However, unlike many other chafer species, the larvae of C. aurata do not pose a threat to agriculture. Auite the opposite in fact: they are detritivores and create very good compost when present in significant numbers in the soil.

Tuesday, July 12, 2011

The aerial acrobatics of the swallow (Hirundo rustica) are something to behold this time of year. The midges and flies that they feed on are in abundance in the summer months, and H. rustica is certainly kitted out to take advantage, with its streamlined wings and long tails. These tails mark them out from similar relatives such swifts and sand martins, as well as the blue-black back and wings, white undersides, red face patch and black breast band (1). It is probably Ireland's most recognisible avian migrant, and certainly its most impressive, traveling from South Africa in early spring to avoid the harsh winters there and returning from Ireland when the cold, autumnal weather reduces the numbers of its invertebrate food.

Swallow, Hirundo rustica

H. rustica is often referred to as the “Barn Swallow” in some countries, due to its habit of nesting in barns and farm outhouses, forming a bowel shaped nest from mud and other materials. It has been shown that in mate selection, females prefer males with long (2), symmetrically patterned tails (3). Long tailed individuals arrive earlier, giving them more choice of mates and symmetrical tails signal lowest degree of fluctuating asymmetry and hence the fittest individuals. It would therefore be expected that long tailed individuals would produce more individuals, which was the case in studies in Denmark and Canada in the 1980's (4). However, genetic analysis of offspring produced showed that long tailed males only fathered 59% of the offspring in their nests compared to 96% of the nestlings of short tailed birds. So while long tailed males mate earlier and are preferred by females, they experience a higher percentage of cuckoldry. Unfortunately for them, it is thought that the very thing that gives them an advantage in attracting a mate in the first place (their long tails) is the ting that is their undoing: long tailed males tend to have less maneuverability when feeding, meaning they have to spend longer hunting for food and consequently less time protecting their mates.

Monday, July 11, 2011

I can understand why people are afraid of spiders. I think its the scurrying movements. Stillness followed by an unpredictable dash. With the smaller, species its not a problem, but when the big boys dart across the semisolid laminate it can cause even the bravest among us a moments terror. Probably the most common culprit in cases in Ireland like this is the impressively sized Common House Spider (Tegenaria domestica), which generally has a body size of 10 mm, but can often be larger. Its is strongly associated with human activities, making webs with funnel entrances in many parts of houses and their external walls. It has a hairy body of variable colour, from pale to dark brown (1).

Common House Spider, Tegenaria domestica

While it is easy to scoff at (some may say irrational) fear of species like T. domestica, there is a health risk with the spider. It is not, as with many spiders worldwide, a risk of being bitten – species of spider in Ireland are not venomous unless you're smaller than a grasshopper – but something more intriguing. In 2005 it was reported (2) that a pig farmer in Tampere, Finland presented to the University Hospital there with eczema on his face, neck and hands. Isolation from and re-exposure to the sty in which he worked revealed the problem to lie there. It was also discovered that there had been an increase in the number of house flies (Musca domestica) in the sty in the past number of years, which had lead to an increase in the numbers of T. domestica. Skin prick tests preformed with T. domestica extract as well as its webbing were positive and Immunoglobulin E (IgE) immunospot tests with spider extract and patient serum proved similarly positive. Indeed the patient proved to be allergic to this species alone and not to any other spider or mites species often associated with similar allergic reactions.

Follow us on Twitter

Follow by Email

About Me

We at the 21stcenturynaturalist hope to engage and provoke interest with our natural history based blogs.
All images featured in this blog are copyrighted to 21stcenturynaturalist. Please email us at 21stcenturynaturalists@gmail.com if you wish to use any images.